EP0077738A1 - Ion source having a gas ionization chamber with oscillations of electrons - Google Patents

Ion source having a gas ionization chamber with oscillations of electrons Download PDF

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Publication number
EP0077738A1
EP0077738A1 EP82401920A EP82401920A EP0077738A1 EP 0077738 A1 EP0077738 A1 EP 0077738A1 EP 82401920 A EP82401920 A EP 82401920A EP 82401920 A EP82401920 A EP 82401920A EP 0077738 A1 EP0077738 A1 EP 0077738A1
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Prior art keywords
electrons
source
lenses
lens
ion source
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EP82401920A
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German (de)
French (fr)
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EP0077738B1 (en
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Robert La Coudounière Boyer
Jean-Pierre Journoux
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns

Definitions

  • the present invention relates to an ion source which can be used, for example, in the analysis of gases by mass spectrometry.
  • a source of ions of a first type which comprises an ionization chamber, a source of electrons constituted by a heating filament (cathode) and a "trap" (anode) opposite.
  • the emitted electrons are accelerated between the filament and the ionization chamber and ionize the molecules of the gas contained in the chamber.
  • a servo system can possibly allow, thanks to the electronic current collected on the anode, to regulate the current circulating in the filament and therefore, to stabilize the flow of electrons emitted towards the ionization zone.
  • a magnetic field directed in the direction of the electron beam channels the electrons and allows better extraction of the ions produced towards an analysis device, such as a mass spectrometer, for example.
  • each electron emitted only crosses the ionization chamber once, when it does not come to ionize a molecule. This results in a low ionization efficiency, lying between 10 and 10. This yield is defined by the ratio of the number of ions formed to the number of electrons emitted.
  • Another characteristic coefficient of the performance of an ion source is defined by the ratio of the number of ions formed to the number of molecules introduced; this coefficient is called "brightness".
  • the brightness of the sources described above is very low ( ⁇ 10 -5 ).
  • Ion sources of a second type are also known, the ionization efficiency and the luminosity are higher than those of the previous sources.
  • These sources include a filament that produces electrons, an accelerating cathode, and an anode that collects electronic current. Between the cathode and the anode is an intermediate electrode and behind the anode is an anticathode. Voltage pulses are applied to the cathode so as to cause a discharge between the cathode and the intermediate electrode. This discharge ionizes the gas. The electrons produced then oscillate in the zone located between the intermediate electrode and the anticathode, zone in which a hollow of potential is created. The electrons cause ionization of the gas in this area.
  • This source has a better yield and better luminosity than the previous source, but its structure is complicated and its implementation very difficult.
  • the aim of the present invention is to remedy the drawbacks of known sources and in particular to produce an ion source in which the electrons oscillate, which has an easier structure and implementation, a higher yield and a higher luminosity than the second. type of source mentioned above.
  • the invention relates to an ion source comprising a gas ionization chamber and, in this chamber, at least one electron source, means for oscillating the electrons from the source in a predetermined direction so creating an ionization zone for the gas, and means for collecting the ions produced, characterized in that the means for oscillating the electrons comprise two identical electronic lenses situated facing each other and whose axes coincide with the predetermined direction, two concave spherical mirrors facing each other and located respectively on either side of the two lenses, so that their centers coincide respectively with the focal points of the lenses, the electron source being located at the focal point of one of the two lenses.
  • each lens is constituted so as to accelerate the electrons reflected by the mirror which corresponds to it and to decelerate the electrons coming from the other lens, the lens whose focus constitutes the location of the source being able to accelerate the electrons emitted by this source.
  • the ion source comprises another electronic source located at the focal point of the other of the two lenses.
  • the lenses are brought to identical electrical potentials.
  • This source includes a 1 re ionization chamber presented schematically and, in this chamber, at least one source of electrons SE 1 and, means for oscillating the electrons coming from the source, in a predetermined direction XX ', so as to create an ionization zone Z of the gas contained in the chamber 1.
  • These means comprise two identical electronic lenses L 1 , L2 , located opposite one another and whose axes coincide with the predetermined direction X'X.
  • These means also include two spherical mirrors M 1 , M 2 , concave, facing one another and located respectively on either side of the two lenses L 1 , L 2 .
  • each lens is formed so as to accelerate the electrons reflected by the mirror which corresponds to it and so as to decelerate the electrons coming from the other lens.
  • the lens L 2 makes it possible to decelerate the electrons which come from the lens L 1 and to accelerate the electrons which are reflected by the mirror L 2 , while the lens L 1 decelerates the electrons coming from the lens L 2 and accelerates the electrons emitted by the source SE 1 or the electrons reflected on the mirror M 1 .
  • Another source of electrons SE 2 identical to the source SE 1 can possibly be placed at the focal point F 2 of the lens L 2 , to supply electrons, in particular in the event of failure of the source SE 1 .
  • the lenses L 1 and L 2 are brought to identical electrical potentials.
  • magnetic pole pieces N and S which possibly allow better focusing of the electrons flowing in the chamber. ionization, but which are not essential. Indeed, the focusing of the electrons can be ensured sufficiently by the lenses D 11 , D 21 ' D 31' D 12 ' D 22 , D 32 .
  • FIG 2 shows in more detail an ion source according to the invention.
  • the same elements have the same references in this figure as in Figure 1. It is assumed that all the elements shown in this figure are cylindrical and that they are seen in section, the openings in these elements being rectangular.
  • the device which is shown here in more detail includes the lenses L 1 and L 2 , the mirrors M l and M 2 ' the electron sources SE 1 and SE 2 , and the magnetic pole pieces N and S.
  • the chamber d Ionization 1 is shown schematically in broken lines.
  • the electron source SE 1 can consist, for example, of a heating filament, not referenced, situated at the focal point F 1 of the lens L 1 and surrounded by an electrode C 1 (Whenelt).
  • the lens L 1 can be constituted by diaphragms D 11 , D 21 , D 31 .
  • the lens L 2 can be constituted by diaphragms D 12 , D 22 , D 32 .
  • the second electronic source SE 2 which is constituted by an unreferenced filament situated at the focal point F 2 of the lens L 2 , and by an electrode C 2 surrounding this filament.
  • the filament, the CloU C electrode (s) 2 and the mirrors M 1 and M 2 are brought to the potential of the filament, close to 0 volts.
  • Diaphragms D 11 and D 32 are brought to a potential close to 280 volts
  • diaphragms D 31 and D 12 which are electrically isolated from the preceding diaphragms, as well as the ionization chamber 1, are brought to a potential close to 190 volts.
  • the dia- p hra g my D 21 and D 22 are brought to a negative potential close to -10 volts.
  • the shape of the oscillating electron beam is shown at 2 in the figure.
  • the ionization zone is the zone between the diaphragms D 31 and D 12 .
  • the ions are extracted thanks to the magnetic field, by a slot 0 located halfway between the lenses L 1 , L 2 and perpendicular to the plane of the figure.
  • FIG. 3 represents the distribution of the potential V along the axis XX 'of the ionization chamber.
  • the potential is constant. This potential is zero in the vicinity of the filament located at the focal point F 1 , then it increases to reach a maximum in the vicinity of the diaphragm D 21 and finally decreases to the vicinity of the diaphragm D 31 , to then stabilize at a constant value in the ionization zone Z, between diaphragms D 31 and D 12 .
  • the potential then increases again between the diaphragms D 12 and D 22 to reach a zero value in the vicinity of the filament located at the focal point F 2 of the lens L 2 .
  • each electron can perform up to 25,000 oscillations.
  • the lifetime of an electron produced by the source of the invention is about 50,000 times longer than the lifetime of an electron produced by known sources.
  • the source of the invention therefore makes it possible, by increasing the path of the electron and its lifetime (thanks to the oscillations), to obtain a yield and a luminosity much higher than those of existing devices since the number of ions formed can being much larger, it also follows that the number of gaseous molecules that can be introduced into the ionization chamber can also be much higher than for known sources.
  • any electron coming from the filament situated at the focal point F 1 of the lens L 1 is focused at the focal point F 2 of the lens L 2 , then leaves in the opposite direction after having been reflected by the mirror M 2 .
  • This electron which then comes from the lens L 2 finds identical conditions with the lens L I and the mirror M 1 .
  • the source which has just been described has many advantages compared to existing sources: the brightness is multiplied by 20, the ionization efficiency is multiplied by 200, the temperature of the chamber is greatly lowered since it goes from 80 ° C at 40 ° C (since it is not necessary to produce as many electrons as with existing devices to ionize the same number of gas molecules).
  • the temperature of the filament itself can be lowered by 500 ° since, for an equal efficiency, the number of electrons emitted by the filament must be lower, while the electric power which is supplied to this filament is twice lower.
  • the electronic emission current is divided by 10, while the average lifetime of the filament goes from 5,000 hours to 2.10 9 hours.

Abstract

L'invention concerne une source d'ions.The invention relates to an ion source.

Cette source comprend une chambre d'ionisation (1) à gaz, une source d'électrons (SE,), des moyens pour faire osciller les électrons dans la chambre de manière à créer une zone d'ionisation (Z) du gaz. Elle est caractérisée en ce que les moyens pour faire osciller les électrons comprennent deux lentilles électroniques (L1, L2) identiques dont les axes coïncident avec la direction d'oscillation, deux miroirs sphériques (M1, M2) concaves tournés l'un vers l'autre et situés respectivement de part et d'autre des deux lentilles (L1, L2) et dont leurs centres coïncident respectivement avec les foyers (F1, F2) des lentilles, la source (SE1) d'électrons étant située au foyer (F,) de l'une des deux lentilles (L1, L2).This source comprises a gas ionization chamber (1), an electron source (SE,), means for oscillating the electrons in the chamber so as to create an ionization zone (Z) of the gas. It is characterized in that the means for oscillating the electrons comprise two identical electronic lenses (L 1 , L 2 ) whose axes coincide with the direction of oscillation, two concave spherical mirrors (M 1 , M 2 ) turned the towards each other and situated respectively on either side of the two lenses (L 1 , L 2 ) and whose centers of the lenses respectively coincide with the focal points (F 1 , F 2 ) of the lenses, the source (SE 1 ) d electrons being located at the focal point (F,) of one of the two lenses (L 1 , L 2 ).

Application à l'analyse des gaz par spectrométrie de masse.

Figure imgaf001
Application to the analysis of gases by mass spectrometry.
Figure imgaf001

Description

La présente invention concerne une source d'ions qui peut être utilisée, par exemple, à l'analyse des gaz par spectrométrie de masse.The present invention relates to an ion source which can be used, for example, in the analysis of gases by mass spectrometry.

On connait une source d'ions d'un premier type, qui comprend une chambre d'ionisation, une source d'électrons constituée par un filament chauffant (cathode) et une "trappe" (anode) en regard.There is known a source of ions of a first type, which comprises an ionization chamber, a source of electrons constituted by a heating filament (cathode) and a "trap" (anode) opposite.

Les électrons émis sont accélérés entre le filament et la chambre d'ionisation et ionisent les molécules du gaz contenu dans la chambre. Un système d'asservissement peut éventuellement permettre, grâce au courant électronique recueilli sur l'anode, de réguler le courant circulant dans le filament et donc, de stabiliser le flux des électrons émis vers la zone d'ionisation.The emitted electrons are accelerated between the filament and the ionization chamber and ionize the molecules of the gas contained in the chamber. A servo system can possibly allow, thanks to the electronic current collected on the anode, to regulate the current circulating in the filament and therefore, to stabilize the flow of electrons emitted towards the ionization zone.

Un champ magnétique dirigé dans le sens du faisceau électronique, canalise les électrons et permet une meilleure extraction des ions produits vers un appareil d'analyse, tel qu'un spectromètre de masse, par exemple.A magnetic field directed in the direction of the electron beam channels the electrons and allows better extraction of the ions produced towards an analysis device, such as a mass spectrometer, for example.

Dans ce type de source, chaque électron émis ne traverse la chambre d'ionisation qu'une seule fois, lorsqu'il ne vient pas ioniser une molécule. Il en résulte un rendement d'ionisation faible, se situant entre 10 et 10 . Ce rendement est défini par le rapport du nombre d'ions formés au nombre d'électrons émis.In this type of source, each electron emitted only crosses the ionization chamber once, when it does not come to ionize a molecule. This results in a low ionization efficiency, lying between 10 and 10. This yield is defined by the ratio of the number of ions formed to the number of electrons emitted.

On définit un autre coefficient caractéristique des performances d'une source d'ions, par le rapport du nombre d'ions formés au nombre de molécules introduites ; ce coefficient est qualifié "luminosité". La luminosité des sources décrites plus haut est très faible (≃10-5).Another characteristic coefficient of the performance of an ion source is defined by the ratio of the number of ions formed to the number of molecules introduced; this coefficient is called "brightness". The brightness of the sources described above is very low (≃10 -5 ).

On connaît aussi des sources d'ions d'un deuxième type dont le rendement d'ionisation ainsi que la luminosité sont plus élevés que ceux des sources précédentes. Ces sources comprennent un filament qui produit des électrons, une cathode accélératrice et une anode recueillant le courant électronique. Entre la cathode et l'anode, se trouve une électrode intermédiaire et derrière l'anode, est disposée une anticathode. Des impulsions de tension sont appliquées à la cathode de manière à provoquer une décharge entre la cathode et l'électrode intermédiaire. Cette décharge ionise le gaz. Les électrons produits oscillent alors dans la zone située entre l'électrode intermédiaire et l'anticathode, zone dans laquelle est créé un creux de potentiel. Les électrons provoquent une ionisation du gaz dans cette zone. Cette source présente un meilleur rendement et une meilleure luminosité que la source précédente, mais sa structure est compliquée et sa mise en oeuvre très difficile.Ion sources of a second type are also known, the ionization efficiency and the luminosity are higher than those of the previous sources. These sources include a filament that produces electrons, an accelerating cathode, and an anode that collects electronic current. Between the cathode and the anode is an intermediate electrode and behind the anode is an anticathode. Voltage pulses are applied to the cathode so as to cause a discharge between the cathode and the intermediate electrode. This discharge ionizes the gas. The electrons produced then oscillate in the zone located between the intermediate electrode and the anticathode, zone in which a hollow of potential is created. The electrons cause ionization of the gas in this area. This source has a better yield and better luminosity than the previous source, but its structure is complicated and its implementation very difficult.

La présente invention a pour but de remédier aux inconvénients des sources connues et notamment de réaliser une source d'ions dans laquelle les électrons oscillent, qui présente une structure et une mise en oeuvre plus faciles, un rendement et une luminosité plus élevés que le deuxième type de source mentionné plus haut.The aim of the present invention is to remedy the drawbacks of known sources and in particular to produce an ion source in which the electrons oscillate, which has an easier structure and implementation, a higher yield and a higher luminosity than the second. type of source mentioned above.

L'invention a pour objet une source d'ions comprenant une chambre d'ionisation à gaz et, dans cette chambre, au moins une source d'électrons, des moyens pour faire osciller les électrons issus de la source dans une direction prédéterminée de manière à créer une zone d'ionisation du gaz, et des moyens pour recueillir les ions produits, caractérisée en ce que les moyens pour faire osciller les électrons comprennent deux lentilles électroniques identiques situées en regard l'une de l'autre et dont les axes coincident avec la direction prédéterminée, deux miroirs sphériques concaves tournés l'un vers l'autre et situés respectivement de part et d'autre des deux lentilles, de sorte que leurs centres coincident respectivement avec les foyers des lentilles, la source d'électrons étant située au foyer de l'une des deux lentilles.The invention relates to an ion source comprising a gas ionization chamber and, in this chamber, at least one electron source, means for oscillating the electrons from the source in a predetermined direction so creating an ionization zone for the gas, and means for collecting the ions produced, characterized in that the means for oscillating the electrons comprise two identical electronic lenses situated facing each other and whose axes coincide with the predetermined direction, two concave spherical mirrors facing each other and located respectively on either side of the two lenses, so that their centers coincide respectively with the focal points of the lenses, the electron source being located at the focal point of one of the two lenses.

Selon une autre caractéristique de l'invention chaque lentille est constituée de manière à accélérer les électrons réfléchis par le miroir qui lui correspond et à décélérer les électrons provenant de l'autre lentille, la lentille dont le foyer constitue l'emplacement de la source étant apte à accélérer les électrons émis par cette source.According to another characteristic of the invention, each lens is constituted so as to accelerate the electrons reflected by the mirror which corresponds to it and to decelerate the electrons coming from the other lens, the lens whose focus constitutes the location of the source being able to accelerate the electrons emitted by this source.

Selon une autre caractéristique, la source d'ions comprend une autre source électronique située au foyer de l'autre des deux lentilles.According to another characteristic, the ion source comprises another electronic source located at the focal point of the other of the two lenses.

Selon une autre caractéristique, les lentilles sont portées à des potentiels électriques identiques.According to another characteristic, the lenses are brought to identical electrical potentials.

D'autres caractéristiques et avantages de l'invention ressortiront mieux de la description qui va suivre donnée en référence aux dessins annexés dans lesquels :

  • - la figure 1 est une vue schématique qui permet de mieux comprendre par analogie et avec un système optique, la structure et le fonctionnement de la source de l'invention ;
  • - la figure 2 représente de manière plus détaillée la source d'ions de l'invention ;
  • - la figure 3 représente la répartition des potentiels le long de l'axe X'X, de la chambre d'ionisation.
Other characteristics and advantages of the invention will emerge more clearly from the description which follows given with reference to the appended drawings in which:
  • - Figure 1 is a schematic view which allows a better understanding by analogy and with an optical system, the structure and operation of the source of the invention;
  • - Figure 2 shows in more detail the source of ions of the invention;
  • - Figure 3 shows the distribution of potentials along the X'X axis of the ionization chamber.

En référence à la figure 1, on a représenté très schématiquement la source d'ions de l'invention. Cette source comprend une chambre d'ionisation 1 représentée de manière schématique et, dans cette chambre, au moins une source d'électrons SE1 et, des moyens pour faire osciller les électrons issus de la source,dans une direction prédéterminée XX', de manière à créer une zone Z d'ionisation du gaz contenu dans la chambre 1. Ces moyens comprennent deux lentilles électroniques L1, L2 identiques, situées en regard l'une de l'autre et dont les axes coïncident avec la direction prédéterminée X'X. Ces moyens comprennent aussi deux miroirs sphériques M1, M2, concaves, tournés l'un vers l'autre et situés respectivement de part et d'autre des deux lentilles Ll, L2. Les centres de ces miroirs coïncident respectivement avec les foyers F1, F2 des lentilles. La source d'électrons SE1 est située par exemple au foyer FI de la lentille L1. Comme on le verra plus loin en détail, chaque lentille est constituée de manière à accélérer les électrons réfléchis par le miroir qui lui correspond et de manière à décélérer les électrons provenant de l'autre lentille. C'est ainsi par exemple que la lentille L2 permet de décélérer les électrons qui proviennent de la lentille L1 et d'accélérer les électrons qui sont réfléchis par le miroir L2,tandis que la lentille L1 décélère les électrons provenant de la lentille L2 et accélère les électrons émis par la source SE1 ou les électrons réfléchis sur le miroir M1. Une autre source d'électrons SE2 identique à la source SE1 peut éventuellement être placée au foyer F2 de la lentille L2, pour fournir des électrons, notamment en cas de panne de la source SE1. Comme on le verra plus loin en détail, les lentilles L1 et L2 sont portées à des potentiels électriques identiques. On a également représenté sur cette figure des pièces polaires magnétiques N et S qui permettent éventuellement une meilleure focalisation des électrons qui circulent dans la chambre d'ionisation, mais qui ne sont pas indispensables. En effet, la focalisation des électrons peut être assurée suffisamment par les lentilles D11, D21' D31' D12' D22, D32.Referring to Figure 1, there is shown very schematically the ion source of the invention. This source includes a 1 re ionization chamber presented schematically and, in this chamber, at least one source of electrons SE 1 and, means for oscillating the electrons coming from the source, in a predetermined direction XX ', so as to create an ionization zone Z of the gas contained in the chamber 1. These means comprise two identical electronic lenses L 1 , L2 , located opposite one another and whose axes coincide with the predetermined direction X'X. These means also include two spherical mirrors M 1 , M 2 , concave, facing one another and located respectively on either side of the two lenses L 1 , L 2 . The centers of these mirrors coincide respectively with the focal points F 1 , F2 of the lenses. The electron source SE 1 is located for example at the focal point F I of the lens L 1 . As will be seen in detail below, each lens is formed so as to accelerate the electrons reflected by the mirror which corresponds to it and so as to decelerate the electrons coming from the other lens. Thus, for example, the lens L 2 makes it possible to decelerate the electrons which come from the lens L 1 and to accelerate the electrons which are reflected by the mirror L 2 , while the lens L 1 decelerates the electrons coming from the lens L 2 and accelerates the electrons emitted by the source SE 1 or the electrons reflected on the mirror M 1 . Another source of electrons SE 2 identical to the source SE 1 can possibly be placed at the focal point F 2 of the lens L 2 , to supply electrons, in particular in the event of failure of the source SE 1 . As will be seen below in detail, the lenses L 1 and L 2 are brought to identical electrical potentials. Also shown in this figure are magnetic pole pieces N and S which possibly allow better focusing of the electrons flowing in the chamber. ionization, but which are not essential. Indeed, the focusing of the electrons can be ensured sufficiently by the lenses D 11 , D 21 ' D 31' D 12 ' D 22 , D 32 .

La figure 2 représente de manière plus détaillée, une source d'ions conforme à l'invention. Les mêmes éléments portent les mêmes référencs sur cette figure que sur la figure 1. On suppose que tous les éléments représentés sur cette figure sont cylindriques et qu'ils sont vus en coupe, les ouvertures dans ces éléments étant rectangulaires. Le dispositif qui est représenté ici de manière plus détaillée comprend les lentilles L1 et L2, les miroirs Ml et M2' les sources d'électrons SE1 et SE2, et les pièces polaires magnétiques N et S. La chambre d'ionisation 1 est représentée de manière schématique en traits interrompus. La source d'électrons SE1 peut être constituée par exemple par un filament chauffant, non référencé, situé au foyer F1 de la lentille L1 et entouré d'une électrode C1 (Whenelt). La lentille L1 peut être constituée par des diaphragmes D11, D21, D31. De la même manière, la lentille L2 peut être constituée par des diaphragmes D12, D22, D32. On a également représenté sur cette figure, la deuxième source électronique SE2 qui est constituée par un filament non référencé situé au foyer F2 de la lentille L2, et par une électrode C2 entourant ce filament. A titre d'exemple, le filament, la ou les électrodes CloU C2 et les miroirs M1 et M2 sont portés au potentiel du filament, voisin de 0 volt. Des diaphragmes D11 et D32 sont portés à un potentiel voisin de 280 volts, les diaphragmes D31 et D12, qui sont électriquement isolés des diaphragmes précédents, ainsi que la chambre d'ionisation 1, sont portés à un potentiel voisin de 190 volts. Les dia- phragmes D21 et D22 sont portés à un potentiel négatif voisin de -10 volts. L'allure du faisceau d'électrons oscillants est représentée en 2 sur la figure. La zone d'ionisation est la zone comprise entre les diaphragmes D31 et D12. Les ions sont extraits grâce au champ magnétique, par une fente 0 située à mi-distance des lentilles L1, L2 et perpendiculaire au plan de la figure.Figure 2 shows in more detail an ion source according to the invention. The same elements have the same references in this figure as in Figure 1. It is assumed that all the elements shown in this figure are cylindrical and that they are seen in section, the openings in these elements being rectangular. The device which is shown here in more detail includes the lenses L 1 and L 2 , the mirrors M l and M 2 ' the electron sources SE 1 and SE 2 , and the magnetic pole pieces N and S. The chamber d Ionization 1 is shown schematically in broken lines. The electron source SE 1 can consist, for example, of a heating filament, not referenced, situated at the focal point F 1 of the lens L 1 and surrounded by an electrode C 1 (Whenelt). The lens L 1 can be constituted by diaphragms D 11 , D 21 , D 31 . Likewise, the lens L 2 can be constituted by diaphragms D 12 , D 22 , D 32 . Also shown in this figure, the second electronic source SE 2 which is constituted by an unreferenced filament situated at the focal point F 2 of the lens L 2 , and by an electrode C 2 surrounding this filament. As an example, the filament, the CloU C electrode (s) 2 and the mirrors M 1 and M 2 are brought to the potential of the filament, close to 0 volts. Diaphragms D 11 and D 32 are brought to a potential close to 280 volts, diaphragms D 31 and D 12 , which are electrically isolated from the preceding diaphragms, as well as the ionization chamber 1, are brought to a potential close to 190 volts. The dia- p hra g my D 21 and D 22 are brought to a negative potential close to -10 volts. The shape of the oscillating electron beam is shown at 2 in the figure. The ionization zone is the zone between the diaphragms D 31 and D 12 . The ions are extracted thanks to the magnetic field, by a slot 0 located halfway between the lenses L 1 , L 2 and perpendicular to the plane of the figure.

La figure 3 représente la répartition du potentiel V le long de l'axe XX' de la chambre d'ionisation. Dans la zone d'ionisation Z comprise entre les diaphragmes D31 et D12, le potentiel est constant. Ce potentiel est nul au voisinage du filament situé au foyer F1, puis il croit pour atteindre un maximum au voisinage du diaphragme D21 et enfin, décroît jusqu'au voisinage du diaphragme D31, pour se stabiliser ensuite à une valeur constante dans la zone d'ionisation Z, entre les diaphragmes D31 et D12. Le potentiel croît alors de nouveau entre les diaphragmes D12 et D22 pour atteindre une valeur nulle au voisinage du filament situé au foyer F2 de la lentille L2. Dans la zone, il y a accumulation d'électrons par paquets, à chaque oscillation et il en résulte une ionisation intense dans cette zone.FIG. 3 represents the distribution of the potential V along the axis XX 'of the ionization chamber. In the ionization zone Z between the diaphragms D 31 and D 12 , the potential is constant. This potential is zero in the vicinity of the filament located at the focal point F 1 , then it increases to reach a maximum in the vicinity of the diaphragm D 21 and finally decreases to the vicinity of the diaphragm D 31 , to then stabilize at a constant value in the ionization zone Z, between diaphragms D 31 and D 12 . The potential then increases again between the diaphragms D 12 and D 22 to reach a zero value in the vicinity of the filament located at the focal point F 2 of the lens L 2 . In the zone, there is an accumulation of electrons in packets, with each oscillation and this results in intense ionization in this zone.

Grâce au dispositif qui vient d'être décrit, chaque électron peut effectuer jusqu'à 25.000 oscillations. La durée de vie d'un électron produit par la source de l'invention est d'environ 50.000 fois plus longue que la durée de vie d'un électron produit par les sources connues. La source de l'invention permet donc, en augmentant le parcours de l'électron et sa durée de vie (grâce aux oscillations) d'obtenir un rendement et une luminosité bien supérieurs à ceux des dipositifs existants puisque le nombre d'ions formés peut être bien plus grand, il en résulte aussi que le nombre de molécules gazeuses que l'on peut introduire dans la chambre d'ionisation peut être lui aussi bien plus élevé que pour les sources connues. En fait, dans la source qui vient d'être décrite, tout électron issu du filament situé au foyer F1 de la lentille L1 est focalisé au foyer F2 de la lentille L2, puis repart en sens inverse après avoir été réfléchi par le miroir M2. Cet électron qui est alors issu de la lentille L2 retrouve des conditions identiques avec la lentille LI et le miroir M1.Thanks to the device which has just been described, each electron can perform up to 25,000 oscillations. The lifetime of an electron produced by the source of the invention is about 50,000 times longer than the lifetime of an electron produced by known sources. The source of the invention therefore makes it possible, by increasing the path of the electron and its lifetime (thanks to the oscillations), to obtain a yield and a luminosity much higher than those of existing devices since the number of ions formed can being much larger, it also follows that the number of gaseous molecules that can be introduced into the ionization chamber can also be much higher than for known sources. In fact, in the source which has just been described, any electron coming from the filament situated at the focal point F 1 of the lens L 1 is focused at the focal point F 2 of the lens L 2 , then leaves in the opposite direction after having been reflected by the mirror M 2 . This electron which then comes from the lens L 2 finds identical conditions with the lens L I and the mirror M 1 .

La source qui vient d'être décrite présente de nombreux avantages par rapport aux sources existantes : la luminosité est multipliée par 20, le rendement d'ionisation est multiplié par 200, la température de la chambre est fortement abaissée puisqu'elle passe de 80°C à 40°C (puisqu'il n'est pas nécessaire de produire autant d'électrons qu'avec les dispositifs existants pour ioniser le même nombre de molécules de gaz). La température du filament lui-même peut être abaissée de 500° puisqu'à rendement égal, le nombre d'électrons émis par le filament doit être moins élevé, tandis que la puissance électrique qui est fournie à ce filament est deux fois plus faible. Le courant d'émission électronique est divisé par 10, tandis que la durée de vie moyenne du filament passe de 5.000 heures à 2.109 heures. Les performances bien meilleures que celles des sources connues et notamment l'augmentation de la luminosité, permettent de fournir des courants d'ions beaucoup plus intenses aux spectromètres de masse et donc d'accroître le rapport signal/bruit. Cet accroissement de la luminosité permet, pour des courants ioniques équivalents à ceux des sources connues, d'utiliser des gaz présentant des pressions bien plus faibles et ainsi, de ménager la durée de vie des sources. La symétrie du dispositif permet d'inverser la source émettrice d'électrons.The source which has just been described has many advantages compared to existing sources: the brightness is multiplied by 20, the ionization efficiency is multiplied by 200, the temperature of the chamber is greatly lowered since it goes from 80 ° C at 40 ° C (since it is not necessary to produce as many electrons as with existing devices to ionize the same number of gas molecules). The temperature of the filament itself can be lowered by 500 ° since, for an equal efficiency, the number of electrons emitted by the filament must be lower, while the electric power which is supplied to this filament is twice lower. The electronic emission current is divided by 10, while the average lifetime of the filament goes from 5,000 hours to 2.10 9 hours. The much better performances than those of known sources and in particular the increase in brightness, make it possible to supply much more intense ion currents to mass spectrometers and therefore to increase the signal / noise ratio. This increase in brightness makes it possible, for ionic currents equivalent to those of known sources, to use gases having much lower pressures and thus to conserve the life of the sources. The symmetry of the device makes it possible to reverse the electron-emitting source.

Claims (4)

1. Source d'ions comprenant une chambre d'ionisation (1) à gaz et, dans cette chambre, au moins une source d'électrons (SE1), des moyens pour faire osciller les électrons issus de la source (SE) dans une direction (X'X) prédéterminée de manière à créer une zone d'ionisation (Z) du gaz, et des moyens pour recueillir les ions produits, caractérisée en ce que les moyens pour faire osciller les électrons comprennent deux lentilles électroniques (Ll, L2) identiques situées en regard l'une de l'autre et dont les axes coincident avec la direction (X'X) prédéterminée, deux miroirs sphériques (M1, M2) concaves tournés l'un vers l'autre et situés respectivement de part et d'autre des deux lentilles (L1, L2), de sorte que leurs centres coïncident respectivement avec les foyers (F1, F2) des lentilles, la source (SE1) d'électrons étant située au foyer (F1) de l'une des deux lentilles (L1, L2).1. Ion source comprising a gas ionization chamber (1) and, in this chamber, at least one electron source (SE 1 ), means for oscillating the electrons coming from the source (SE) in a direction (X'X) predetermined so as to create an ionization zone (Z) of the gas, and means for collecting the ions produced, characterized in that the means for oscillating the electrons comprise two electronic lenses (L l , L 2 ) identical situated opposite one another and whose axes coincide with the predetermined direction (X'X), two concave spherical mirrors (M 1 , M 2 ) turned towards each other and located respectively on either side of the two lenses (L 1 , L 2 ), so that their centers coincide respectively with the focal points (F 1 , F 2 ) of the lenses, the source (SE 1 ) of electrons being located at the focus (F 1 ) of one of the two lenses (L 1 , L2). 2. Source d'ions selon la revendication 1, caractérisée en ce que chaque lentille (L1) est constituée de manière à accélérer les électrons réfléchis par le miroir qui lui correspond (M1) et à décélérer les électrons provenant de l'autre lentille (L2), la lentille (L1) dont le foyer (F1) constitue l'emplacement de la source (SE1) étant apte à accélérer les électrons émis par cette source.2. Ion source according to claim 1, characterized in that each lens (L 1 ) is constituted so as to accelerate the electrons reflected by the mirror which corresponds to it (M 1 ) and to decelerate the electrons coming from the other lens (L 2 ), the lens (L 1 ) whose focal point (F 1 ) constitutes the location of the source (SE 1 ) being able to accelerate the electrons emitted by this source. 3. Source d'ions selon la revendication 1, caractérisée en ce qu'elle comprend une autre source électronique (SE2) située au foyer (F2) de l'autre (L2) des deux lentilles.3. Ion source according to claim 1, characterized in that it comprises another electronic source (SE 2 ) located at the focus (F 2 ) of the other (L 2 ) of the two lenses. 4. Source d'ions selon la revendication 2, caractérisée en ce que les lentilles (L1, L2) sont portées à des potentiels électriques identiques.4. Ion source according to claim 2, characterized in that the lenses (L 1 , L 2 ) are brought to identical electrical potentials.
EP82401920A 1981-10-21 1982-10-19 Ion source having a gas ionization chamber with oscillations of electrons Expired EP0077738B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8119761A FR2514946A1 (en) 1981-10-21 1981-10-21 ION SOURCE COMPRISING A GAS IONIZATION CHAMBER WITH ELECTRON OSCILLATIONS
FR8119761 1981-10-21

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EP0077738A1 true EP0077738A1 (en) 1983-04-27
EP0077738B1 EP0077738B1 (en) 1986-02-26

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WO1986006922A1 (en) * 1985-05-09 1986-11-20 The Commonwealth Of Australia Plasma generator
US5028791A (en) * 1989-02-16 1991-07-02 Tokyo Electron Ltd. Electron beam excitation ion source
US4933551A (en) * 1989-06-05 1990-06-12 The United State Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Reversal electron attachment ionizer for detection of trace species
US5017780A (en) * 1989-09-20 1991-05-21 Roland Kutscher Ion reflector
DE69609358T2 (en) * 1996-09-27 2000-12-14 Arpad Barna ION SOURCE FOR GENERATING IONS FROM GAS OR VAPOR
US7323682B2 (en) * 2004-07-02 2008-01-29 Thermo Finnigan Llc Pulsed ion source for quadrupole mass spectrometer and method
JP2009507328A (en) * 2005-05-11 2009-02-19 イメイゴ サイエンティフィック インストゥルメンツ コーポレイション Reflectron

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JPS5880255A (en) 1983-05-14
EP0077738B1 (en) 1986-02-26
FR2514946B1 (en) 1983-12-02
FR2514946A1 (en) 1983-04-22
DE3269440D1 (en) 1986-04-03
US4468564A (en) 1984-08-28

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